1.5 cell division and protein control Flashcards
Cytoskeleton definition
The cell organelle which provides mechanical support, shape and the ability to control the movement of membrane bound organelles around a cell.
What is the cytoskeleton made up of
Microtubules which are made up of tubulin
Where does the cytoskeleton come from
The MTOC (microtubule organising centre)
Or called the centrosome
What forms the spindle fibres in mitosis
Microtubules
Mitotic index
The number of cells undergoing mitosis
PMAT /total cells x100
What happens to the cytoskeleton in mitosis
It’s remodelled
Cell cycle parts
Interphase
Mitotic phase
Interphase sub phases
G1
S
G2
Mitotic phase sub phases
Mitosis
Cytokinesis
Polymerisation of tubulin
Where tubulin is built up into parts of the cytoskeleton
Depolymerisation of Tubulin
Where the cytoskeleton is broken down into tubulin.
G1 phase
A growth period where proteins and organelles are synthesised
S phase
DNA is replicated for mitosis
G2 phase
A second growth period where proteins and organelles for mitosis are synthesised
Mitosis
Where chromosomes are separated by spindle fibres
Cytokinesis
Where the cytoplasm will divide
Mitosis stages
Prophase
Metaphase
Anaphase
Telophase
Prophase
DNA condenses into 2 pairs of chromosomes which each contain 2 sister chromatids, the nuclear membrane breaks down and spindle fibres will attach to the chromosomes at the kinetochore
Metaphase
The chromosomes will line up on the equator
Anaphase
Spindle fibres depolymerise and pull sister chromatids apart, pulling chromosomes to opposite poles of the cell
Telophase
Chromosomes decondense and nucearnmemebranse form at each pole.
Microtubule function in cell cycle
Aligning chromosomes on equator
Separate sister chromatids
Formation of daughter nuclear membrane
Cell cycle checkpoints
G1 checkpoint
G2 checkpoint
M checkpoint
G2 checkpoint occurrence
End of G2
G1 checkpoint occurrence
End of G1
M checkpoint occurrence
between metaphase and anaphase
G1 checkpoint purpose
To ensure sufficient cell growth
G2 checkpoint purpose
To ensure success of DNA replication in S and ensure no damage is done to DNA
M checkpoint purpose
Occurs during metaphase and controls entry to anaphase ensuring the chromosomes line up correctly on the equator. Meaning daughter cells will receive correct number of chromosomes
G0
A non dividing phase which cells go into if they fail the G1 checkpoint
Checkpoint regulating proteins
Cyclin dependent kinases (CDK)
How do CDK’s regulate the phases of cell cycle
Cyclin proteins accumulate during the phases of cell cycle then they combine and activate cyclin dependent kinases
Then the CDK’s will phosphorylate proteins which regulate cell cycle.
If sufficient threshold of regulating proteins is reached the cell willmove onto onto the next stage of cell cycle
Retinoblastoma
A protein which acts as a tumour suppressor by inhibiting transcription of genes that code for proteins in DNA replication
What state is retinoblastoma in at G1
Active
CDK’s method of moving out of G1
CDK’s will phosphorylate and deactivate retinoblastoma this will allow for transcription factors to bind to DNA and promote DNA replication allowing the cell to move into S
What triggers p53
DNA damage
p53 options
Repair
Arrest the cell cycle
Initiate apoptosis
Uncontrolled reduction in cell cycle
Degenerative disease
Proto - oncogene definition
A normal gene which is involved in the control of cell growth or cell division which mutates to form a tumour forming oncogene.
What does excessive apoptosis lead to
Degenerative diseases
Uncontrolled increase in the cell cycle
Tumour formation
Apoptosis
Programmed cell death
What does lack of apoptosis lead to
Tumour formation or cancer
Types of apoptosis
External or internal
Extrinsic (external) cell death
Lymphocytes or natural killers will send signal molecules to bind with receptors on the surface of the cell membrane.
Intrinsic (internal) cell death
Factors such as DNA damage or lack of growth factor can cause p53 tumour suppressor protein to activate intrinsic apoptosis.
Caspases definition
A type of protease enzyme which breaks down proteins and causes cell destruction
What happens after apoptosis signal in apoptosis
Other uses of apoptosis
To remove cells which are no longer required as development progresses, an example is fingers during metamorphosis
